The present invention relates generally to a read/write head assembly for use in a computer data storage drive, and in particular, to a read/write head having a conductive lead arrangement for providing a substantially planar surface on which to form an inductive write element.
State of the art thin film read/write structures in data storage systems generally include an inductive write head in combination with either an inductive or magnetoresistive (MR) read head.
One type of MR/inductive write head arrangement includes an inductive write head assembly formed adjacent to a magnetoresistive read head subassembly, separated by a layer of gap material. The read head includes an MR element and corresponding MR leads in a "read gap" formed by two soft magnetic shielding layers. The MR element and leads are electrically isolated from the shielding layers by an insulating material in the read gap. The write head includes an inductive coil, a magnetic yoke having upper and lower pole pieces which surrounds a portion of the coil, and insulating material within the yoke to electrically isolate the yoke from the coil. This type of read/write head assembly is sometimes referred to as a "piggy-back" structure.
In a second known MR/inductive head combination, the lower pole of the magnetic yoke also serves as one of the shielding layers of the read assembly. Such an arrangement is commonly referred to as a "merged" head design.
One disadvantage of the layered structures described above is the uneven or "stepped" topography beneath the inductive coil. The unevenness is primarily due to the protrusion of the lower pole piece. Although step abruptness is smoothed to some degree by a layer of insulating material beneath the coil, substantial unevenness remains. Consequently, formation of the coil may result in notched or broken resist lines along the step ridges, adversely affecting write head performance and yield.
It is therefore desirable to provide a substantially even, planar surface beneath the inductive coil. U.S. Pat. No. 4,855,854 suggests a planarization process wherein insulation layers applied before and after the formation of an inductive coil are mechanochemically polished to correct unevenness. This solution, however, introduces additional steps to the manufacturing process.
In an alternative solution the lower pole piece is extended along the entire length of the substrate to form a planar surface beneath the inductive coil. In a merged head design, however, such a pole extension increases the risk of shorting between the lower pole piece and the shielding layer of the "piggy-back" head or the MR leads of the "merge" head.
A further disadvantage of the "piggy-back" and "merged" head designs is the required dimensions of the MR leads. In previous designs, the MR leads extended beyond the perimeter of the inductive coil to enable electrical contact with read terminal pads external to the head assembly. But as read gaps become smaller, the problems of lead resistance and electrical shorting between the leads and the shielding layers of the "piggy-back" head, or between the leads and the shielding layer and lower pole piece of the "merged" head become greater concerns. It is therefore desirable to reduce the length and total area of the MR leads.
Yet another disadvantage of the previous designs is the necessity for an overpass connector to the inner coil tap. The overpass connection may compromise slider height reduction in disk drives with small slider height tolerances.
Read/write assemblies are generally formed on either a central or side rail of a slider. In a known center rail arrangement, terminal pads are typically connected to the MR leads and coil taps in a "write-read-read-write" (WRRW) pattern. However, design constraints may require any arbitrary terminal pad arrangement. This may be the case for either center rail or side rail designs. It is therefore desirable to develop a read-write head assembly having a conductive planarizing layer which easily facilitates a variety of terminal pad arrangements, and is adaptable to either center rail or side rail designs.